The fact that you have a medical marijuana prescription does not mean that you have unlimited rights to use marijuana in public. Since marijuana possession and use is still illegal under federal law, property owners have been put in a tough spot. The feds have been sending out letters to landlords, notifying them that if they do not control the use of marijuana, they could lose their property.
I suggest you look for alternatives rather then blatantly smoke where others can see or smell.
There are smokeless inhalers available. You could also limit your smoking to indoors and use a fan or vent. Or, you can use the non smoke products, such as cookies, brownies, etc.
To find out more about your rights, check with one of the medical marijuana advocacy groups - I posted a link to one of them below.